Direct geological information in Antarctica is limited to ice free regions along the coast, high mountain ranges or isolated nunataks. Therefore, indirect methods are required to reveal subglacial geology and heterogeneities in crustal properties, which are critical steps towards interpreting geological history. We present a 3D crustal model of density and susceptibility distribution in the Wilkes Subglacial Basin and the Transantarctic Mountains (TAM) based on joint inversion of airborne gravity and magnetic data. The applied “variation of information” technique enforces a coupling between gravity and magnetic sources to give an enhanced inversion result. Our model reveals a large-scale body located in the interior of the Wilkes Subglacial Basin interpreted as a batholithic intrusive structure, as well as a linear dense body at the margin of the Terre Adélie Craton. Density and susceptibility relationships are used to inform the interpretation of petrophysical properties and the reconstruction of the origin of those crustal blocks. The petrophysical relationship indicates that the postulated batholitic intrusion is granitic, but independent from the Granite Harbour Igneous Complex previous described in the TAM area. Emplacement of a large volume of intrusive granites can potentially elevate local geothermal heat flow significantly. Finally, we present a tectonic evolution sketch based on the inversion results, which includes development of a passive continental margin with seaward dipping basalt horizons and magmatic underplating followed by two distinct intrusion events in the Wilkes Subglacial Basin with Pan-African ages (700 - 551 Ma) and Ross ages (550 - 450 Ma).

The shapes and directionality of bathymetry at slow-spreading ridges are key to understanding the magmatic or tectonic emplacement of the crust. Magmatic terrain is marked by linearly fault-bounded abyssal hills, while tectonic terrain is marked by long-lived detachment faults, forming Oceanic Core Complexes (OCCs). However, the quantitative description of these crustal regimes is still limited. We develop a novel automated terrain classification technique and test it at the 13-15° N section of the Mid-Atlantic Ridge. The algorithm uses the Slope-Weighted Eccentricity (SWE) of the horizontal eigenvalues to represent surface directionality and reveal crustal tectonic fabric. The application of this new technique yields results consistent with qualitative interpretation. Thus, it provides both new insights into the mid-oceanic ridge spreading and the potential to automate such mapping with different sets of grids, such as gravity and magnetic data in regions further away from the ridge where sediments mask sea-bed features.

The Transantarctic Mountains (TAM) separate the warmer lithosphere of the West Antarctic rift system and the colder East Antarctic craton. Low velocity zones beneath the TAM imaged in recent seismological studies have been interpreted as warm low-density mantle material, suggesting a strong contribution of thermal support to the uplift of the TAM. We present new Curie Depth Point (CDP) and geothermal heat flow (GHF) maps of the northern TAM and adjacent Wilkes Subglacial Basin (WSB) based on high resolution magnetic airborne measurements. We find shallow CDP and high GHF, beneath the northern TAM reinforcing the idea of thermal support of the topography of the mountain range. Additionally, locally high GHF is observed in the Central Basin of the WSB and the Rennick Graben, which has not been resolved previously, while the broader WSB show lower GHF. Across the study area the GHF values range from 30 to 110 mW/m2. Lastly, we compare our CDP estimates to recent Moho depth estimates and our GHF estimates to sparse in situ GHF measurements as well as to existing continent-wide GHF estimates, which shows closed agreement to previous seismic estimates.

In recent years it has been recognised that parts of slow spreading ridges such as the Mid-Atlantic Ridge (MAR) are characterised by typical magmatic spreading, while other parts are characterised by the formation of detachment faults and Oceanic Core Complexes (OCC). These different spreading modes can be clearly identified in the near-ridge environment in the bathymetry, with magmatic mode crust characterised by linear fault-bounded ridges, and detachment mode crust by more chaotic bathymetric signatures. The aim of this project is to characterise the magnetic and gravity signatures of lithosphere created by different modes of spreading, with the aim of using these signatures to identify if the structures still remain in ocean-continent transitions, where they have been covered by sediments coming from the continental crust. We first characterise different modes of spreading using available high-resolution bathymetry data of the MAR up to 20 My of age. The identified characteristics are then related to the corresponding ship-borne gravity and magnetic data in the same area. From the gravity anomalies, thinner crust is observed where the OCCs are in place. This allows the mantle to be exhumed to the sea-floor. As for the magnetic anomalies, it is found that in places where OCCs are present, the anomalies are not as symmetrical as those found in magmatic mode regions. We present a range of parameters extracted from the data that characterise different spreading modes, and use these to test whether transitions between detachment and magmatic mode crust identified in the bathymetry can be readily identified in gravity and magnetic data.